1. Field of the Invention
The present invention relates to transfer of an article in an overhead transportation system.
2. Description of the Related Art
As a problem of the overhead transportation system, when an overhead shuttle (OHS: Over Head Shuttle) is stopped on a travel route for transfer of an article, the travel route is blocked by the overhead shuttle, and a traffic jam may occur. In this regard, according to the disclosure of JP2006-224944A, buffers are provided below a travel rail for a first overhead shuttle, and the first overhead shuttle transfers articles only to or from the buffers. Further, a second overhead shuttle that travels along another travel rail transfers articles between the buffers and stations. In this case, since the article is transferred between the first overhead shuttle and the buffer by elevating and lowering an elevation frame, the first overhead shuttle is stopped above the buffer for a long period of time. In the meanwhile, the travel route is blocked by the first overhead shuttle.